===== mii-tool =====

I use:
  /sbin/mii-tool --force 10baseT-HD eth0

mii-tool works on 10/100 but not on 1000, for that you need ethtool. 

(Steve Wagor)

mii-tool is already in net-tools package in Debian.

===== ethtool =====
Download source of ethtool
 http://directory.fsf.org/All_Packages_in_Directory/ethtool.html
compile it and install it.

On wrap you must set it as follows:

  ethtool -s eth0 autoneg off
  ethtool -s eth0 speed 10 duplex full

i.e turn off autoneg!! 
(Beat Meier)

Or to get ethtool from Debian apt-get repository.